Conventionally, this type of device has a configuration that a friction member whose friction is higher than an inter-sheet friction is arranged on an opposing surface to a supply roller on a stacking pallet to get a sheet pressed and contacted against the supply roller such that sheets on the stacking pallet is supplied one by one from a sheet located on the top in order as a separation part in a case where remaining of sheets stacked on the stacking pallet is small (see Japanese Laid-Open Patent Application No. 2011-201692, page 10, FIG. 8).
However, with the configuration of the conventional device, sheets are accurately supplied one by one. As a result, when a medium such as an envelope that has a pocket-like structure made of two sheets of paper is supplied, a problem may occur. In other words, when an envelope located on the bottom of a pile of stacked envelopes is supplied, a bottom side sheet of the envelope that contacts the friction member and a top side sheet thereof that contacts the supply roller are separated, and then the top and bottom side sheets are supplied as it makes a difference in carried amounts of the sheets in a supply traveling direction. However, because ends of the top and bottom side sheets are connected, a front end and a rear end in the direction are distorted due to the difference in the carried amounts in the traveling direction. Therefore, when distortion of the envelope is increased as the envelope is carried, the distorted ends may contact and give pressure on a sheet running guide therearound and may be got into a carrying roller on a downstream side. Then, a transferring ability may be deteriorated and paper jamming and skew may occur.
A sheet supply device disclosed in the application includes a medium loading part that includes a medium loading surface on which medium is loaded; and a medium supply part that is arranged facing the medium lading surface, and sandwiches the medium with the medium loading part applying a pressure to the medium, and sends the medium loaded in the medium loading part in a predetermined carrying direction. The medium loading part includes a first friction member that is arranged in a position facing the medium supply part so that the first friction member contacts the medium supply part when there is no medium on the medium loading part, and a second friction member that is arranged on an upstream side of the first friction member in the carrying direction, and a friction coefficient (μd) between the second friction member and the medium is larger than a friction coefficient (μc) between the first friction member and the medium.
According to the present invention, distortion when envelopes are supplied is kept to a minimum, so that occurrence of paper jamming and skew during carriage is suppressed.